Eduqas A-Level Chemistry A410QS
Formulae and Equations
Basic Ideas About Atoms
Chemical Calculations
Bonding
Solid Structures
The Periodic Table
Simple Equilibria and Acid-Base Reactions
Thermochemistry
Rates of Reaction
The Wider Impact of Chemistry
Organic Compounds
Hydrocarbons
Halogenoalkanes
Alcohols and Carboxylic Acids
Instrumental Analysis
Redox and Standard Electrode Potential
Redox Reactions
Chemistry of the P-Block
Chemistry of the D-Block Transition Metals
Chemical Kinetics
Enthalpy Changes for Solids and Solutions
Entropy and Feasibility of Reactions
Equilibrium Constants
Acid-Base Equilibria
Stereoisomerism
Aromaticity
Alcohols and Phenols
Aldehydes and Ketones
Carboxylic Acids and Their Derivatives
Amines
Amino Acids, Peptides and Proteins
Organic Synthesis and Analysis
Specified Practical Work
Practical Skills and Techniques
Mathematical Skills in Chemistry
Hydrocarbons
Tests for alkenes
- 2 things to know
- Components 1 and 2
Overview
Observed when bromine water is shaken with an alkane, main organic product formed when bromine water reacts with ethene and why the bromine test distinguishes an alkene from an alkane.
What you need to know
Answer each one before you reveal it.
What is observed when bromine water is shaken with an alkane?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Describe the colour change seen when bromine water is added to an alkene.
Model answer
The orange colour of the bromine water is decolourised almost at once.
- 2
What is observed when bromine water is shaken with an alkane?
Model answer
The orange colour remains, because no reaction takes place in the dark.
- 3
Name the main organic product formed when bromine water reacts with ethene.
Model answer
The main product is 2-bromoethanol, formed because water as well as bromide competes to attack the intermediate.
- 4
What colour change is seen when bromine dissolved in an organic solvent is added to cyclohexene?
Model answer
The orange-brown colour of the solution disappears.
- 5
Explain why the bromine test distinguishes an alkene from an alkane.
Model answer
The π electrons of the double bond polarise and attack the bromine molecule so the coloured bromine is used up, while a saturated alkane offers nothing to react with it at room temperature in the dark.
- 6
Describe what is seen when acidified potassium manganate(VII) solution is shaken with an alkene.
Model answer
The purple colour of the manganate(VII) fades and the solution becomes colourless.
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